Method and apparatus for producing laminate board

ABSTRACT

A method of producing a laminate board (10) involves the steps of heating a continuous belt-like metallic sheet (2) by a heating furnace (1), laminating a thermoplastic resin film (3) on at least one of the surfaces of the metallic sheet, pressing and passing both of them between a pair of laminate rolls (4 and 5), and thermally bonding the film (3) to the metallic sheet (2), wherein the laminate sheet (10) coming out from between the pair of laminate rolls (4 and 5) is pushed by a deflector roll (6) in a transverse direction so as to bias the travelling direction towards the laminate roll (4) in contact with the film (3). The invention also discloses an apparatus (A) used for his method.

TECHNICAL FIELD

The present invention relates to a manufacturing method for a laminatesheet and manufacturing apparatus therefor, and more particularly to amanufacturing method for a laminated sheet, in which a thermoplasticresin film is made to contact and be pressed to a heated metal sheet,and a manufacturing apparatus for carrying out the manufacturing method.

BACKGROUND TECHNOLOGY

As shown in FIG. 4, there is a well known laminating method in which ametal sheet 101, heated in an oven, is then made to contactthermoplastic resin films 102, and the metal sheet 101 and resin films102 are both pressed by a couple of laminating rolls (nip rolls) 103 and104 while the film 102 is partially melted by the heat of metal sheet101 to adhere to metal sheet 101 (see Laid-Open Japanese Patent Hei4-201237, for example). In such a laminating method, the thickness ofthe melted portion of film 102 (thickness of a melted layer), and theadhering strength of film 102 to the metal sheet 101 can be controlledto some extent by selecting conditions such as heating temperature ofmetal sheet 101, distance from the oven to laminating rolls 103 and 104,traveling speed of metal sheet 101, and melting temperature of film 102.

In the conventional method mentioned above, as shown in FIG. 5, forexample, in the case of laminating an oriented resin film when film 102is pressed to the metal sheet 101 by laminating rolls 103 and 104 (seeFIG. 4), the high temperature of the metal sheet 101 is transferred tothe laminating roll 103 of a low temperature through film 102. While thehigh temperature causes the film 102 to form a melted layer 105, thepressed metal sheet 101 and film 102 adhere to each other. After passingthrough the nip between laminating rolls 103 and 104, metal sheet 101 isfree from pressure, and the film surface is not further cooled, and thenthe temperature from the metal sheet is transferred to the whole film,which controls the orientation of oriented layer 106 of the film.Therefore, as the traveling speed of metal sheet 101 and film 102increase, the temperature of the metal sheet should be lowered in orderto control the orientation of the oriented layer because the coolingeffect by the laminating rolls is not sufficient. For this reason, it isdifficult to perform high speed lamination by the conventionallaminating method.

On the other hand, as a method to increase the melted layer by highspeed lamination, heating metal sheet 101 to a higher temperature may beapplied. But in this case, cooling by the laminating rolls does notfully effect cooling of the film 102 so that the melted layer 105 may beformed throughout the whole film thickness, thus reducing the strengthof the film. In addition, in a case where the laminate forms a food canand such wholly melted film is located inside of the formed can, andwhen content is packed and storaged in it, the film is easily cracked byouter impact, which often causes the packed contents to become spoiled.

It is the first object of the present invention to solve the problem inthe conventional method and to provide a manufacturing method for alaminated sheet in which the laminated sheet has its adhesion increased,and the sufficiently increased adhesion can be obtained even by highspeed lamination. The second object of the present invention is toprovide a manufacturing apparatus for such a manufacturing method.

DISCLOSURE OF THE INVENTION

The manufacturing method for a laminate sheet of the present inventionis characterized by the steps of: heating a continuous metal sheet;making a thermoplastic resin film contact at least one surface of it;and passing both the metal sheet and the thermoplastic resin filmthrough the nip of a couple of laminate rolls and pressing the sheet andfilm together, thus thermally bonding the thermoplastic resin film tothe metal sheet. It is further characterized by pressing the laminatesheet, which has passed between the laminate rolls, in a transversedirection so as to deviate the traveling direction to either one of thelaminate rolls. Furthermore, the method of the present invention ischaracterized by deviating the traveling direction of the laminate sheettoward the laminating roll which contacts the thermoplastic resin film.

The manufacturing apparatus for a laminate sheet of the presentinvention is characterized by a heating device for heating a metalsheet, a supplying device for supplying a thermoplastic resin film to belaminated onto at least one side of the heated metal sheet, a couple oflaminate rolls for pressing together the metal sheet and thethermoplastic resin film, and a deflector roll for deviating thetraveling direction of the laminate sheet which has passed through thenip between the couple of laminate rolls to a direction transverse tothe original traveling direction by pushing it aside in the direction ofone of the laminate rolls.

The apparatus of the present invention may further comprise a guide rollfor making the travelling direction of laminate sheet, which is deviatedby the deflector roll, back to the original travelling direction.

The apparatus may also comprise a deflector roll movably arranged in adirection transverse to the traveling direction of the laminate sheet.

Furthermore, the apparatus may effectively comprise a presser orpressure roll for increasing the contact force of the laminate roll andthe laminate sheet when the laminate sheet, which has passed through thelaminate rolls, is pushed aside to one of the laminate rolls.

When pushing the laminate sheet which has passed between the laminaterolls aside toward one of the laminate rolls, the laminate sheet windspartly around such laminate roll by a certain angle. During travelingthe distance corresponding to the arc of that angle, the laminate sheetcontacts that laminate roll with some holding strength due to its owntension and in the meantime the laminate sheet is cooled. Therefore, themetal sheet can have its initial temperature selected higher, whichpermits a melted layer to be thicker during that traveling period. Thus,the thermoplastic resin film and the metal sheet can be more reliablyadhered to each other by the pressing force also during that travelingperiod.

Since the manufacturing apparatus is provided with a deflector roll todeviate the traveling direction of the laminate sheet which has passedbetween the couple of laminate rolls, it is possible to deviate thetraveling direction without causing any resistance to the traveling ofthe laminate sheet. Apparatus provided with a guide roll to take thedeviated traveling direction back to the original direction can easilybe combined with a conventional manufacturing line for a laminate sheet.Further, the apparatus provided with the deflector roll movably arrangedin a direction transverse to the original traveling direction of thelaminate sheet makes it possible to obtain the most preferable thicknessof the melted layer of the film depending on the kind of raw materialand the traveling speed of the laminate sheet so that the adhesivestrength of the film can be improved to thereby prevent subsequentdelamination.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a schematic front view showing one example of themanufacturing apparatus for a laminate sheet of the present invention.

FIG. 2 is a partial cross section of FIG. 1.

FIG. 3(a) is a graph showing the relationship between the period of timeduring which the film contacts the laminate roll according to thepresent invention and the thickness of its melted layer, and

FIG. 3(b) is a graph showing the relationship between the thickness ofthe melted layer and the adhesive strength of the film.

FIG. 4 is a schematic front view showing one example of the conventionalmanufacturing apparatus.

FIG. 5 is a partial cross section of FIG. 4.

FIG. 6 is a schematic front view showing another example of themanufacturing apparatus of the present invention.

THE BEST MODE FOR CARRYING OUT THE INVENTION

Next, the manufacturing method and the manufacturing apparatus for alaminate sheet of the present invention will be explained in more detailreferring to each Figure.

FIG. 1 is a schematic front view showing one example of themanufacturing apparatus of the present invention. FIG. 2 is a partialcross section of FIG. 1. FIG. 3(a) is a graph showing the relationshipbetween the period of time during which the film contacts the laminateroll according to the present invention and the thickness of its meltedlayer, and FIG. 3(b) is a graph showing the relationship between thethickness of the melted layer and the adhesive strength of the film(after forming). FIG. 6 is a schematic front view showing anotherexample of the manufacturing apparatus of the present invention.

In the manufacturing apparatus A for a laminate sheet shown in FIG. 1, ametal sheet 2 passes through an oven 1 and is heated continuously, and acouple of laminate rolls 4 and 5 arranged below oven 1 serve to pressand adhere film 3 to metal sheet 2 coming out from the oven 1. At ashort distance below the laminate rolls 4 and 5 is arranged a rotatabledeflector roll 6 laterally movable in a direction as shown by arrows P1and P2. Further below deflector roll 6 is arranged a rotatable guideroll 7. The rotation axes of laminate rolls 4 and 5, deflector roll 6and guiding roll 7 are parallel to each other. Quenching tank 8containing a quenching liquid is arranged below guide roll 7.

Manufacturing apparatus A' of FIG. 6 is the one provided with hold downpressure roll 9 for pressing laminate sheet 10 against laminate roll 4additionally to manufacturing apparatus A. Pressure roll 9 is rotatableand arranged parallel to laminate roll 4.

As oven 1, there can be used a conventionally known one such as adielectric heating oven. Another heating device such as a heating rollor an induction heating coil can also be used instead of oven 1. Thelaminate rolls 4 and 5 are prior known ones that act as nip rolls forpinching and pressing metal sheet 2 and film 3 running through the nipbetween them. Normally, laminate rolls 4 and 5 are each synchronouslyrotated in opposite directions (arrow S1 and S2) so as to move thelaminate sheet 10 downwardly. The distance between the laminate rolls isadjustable and rotation speed can also be controlled.

Deflector roll 6 has its ends rotatably supported by bearings (notshown), and the bearings are each synchronously movable in thedirections of arrows P1 and P2 using a control cylinder or the like. Thepositions of the bearings are normally adjusted according to apredetermined laminating condition, but they may be adjusted during thelaminating operation. The deflector roll supporting bearings and thusthe deflector roll 6 itself are arranged to move straight andreciprocitively in a lateral direction perpendicular to the surface ofthe laminate sheet. Such bearings can also be arranged for the deflectorroll 6 to rotate about an axis Q which is positioned below (or above)the illustration positions, that is, with the various possible positionsof the axes being parallel to one another. The bearings may bepositioned as shown by the imaginary line.

Guide roll 7 has its ends supported by bearings (not shown), and thebearings are each fixed to a frame or the like. Guide roll 7 is arrangedat such a position as to contact a tangential line N of laminate rolls 4and 5. Not shown is an additional drive or nip roll to drive thelaminate sheet 10 into and out from quenching tank 8. This causestension on the laminate sheet 10, and thus a proper tension works thelaminate sheet 10 located between laminate rolls 4 and 5 and guide roll7.

The manufacturing apparatus constructed as mentioned above is used asfollows. At first, two films 3 and 3 taken out from a supplying devicewhich is not shown are made to contact both sides of the metal sheetthat has passed through oven 1, and then the three members are passedthrough the nip of laminate rolls 4 and 5. Subsequently, the thusproduced laminate sheet 10 is passed on the left side of deflector roll6 which is deviated to the left side from tangential line N shown inFIG. 1, and then it is passed on the right side of guide roll 7, tothereby take the traveling direction back to the original travelingdirection. The deviation distance of deflector roll is suitably adjustedaccording to forming conditions and so on. Further, the laminate sheet10 is guided downward into quenching tank 8.

As mentioned above, since the laminate sheet 10 coming from laminaterolls 4 and 5 travels in a zigzag line, the laminate sheet 10 windspartly around one laminate roll 4 by a predetermined winding angle(contacting angle) θ. Contacting angle θ becomes larger when deflectorroll 6 is deviated to the left illustrated position in FIG. 1, while itbecomes smaller when deflector roll 6 is deviated to its rightillustrated position. When the deviation becomes "0", the laminate sheetis guided downward straight as is conventional, and winding anglebecomes 0.

Thus, a pressing force due to the tension of laminate sheet 10 is workedbetween film 3 and metal sheet 2 by making laminate sheet 10 contactwith one laminate roll 4 by a predetermined winding angle to therebyincrease the period for cooling the laminate sheet. Further in the casewhere the presser roll 9 shown in FIG. 6 is provided, a greater pressingforce can be provided therefore increasing further the contact betweenthe roll 4 and the laminate sheet 10, which can additionally improve thecooling effect due to better thermal conduction.

Since an increase of the cooling is due to the increase of the appliedpressing force between film 3 and metal sheet 2, it affects not onlyfilm 3 which contacts one laminate roll 4 but also film 3a contactingthe other side of metal sheet 2 shown by the imaginary line in FIG. 2.The greater pressing force and the longer the period for contacting thelaminate roll 4, the more the total mass of thermal conductionincreases. Therefore, the initial temperature of metal sheet 2 can beraised due to the increase of the cooling period, and thickness W ofmelted layer 11 on the side of the film 3 contacting the metal sheet 2can be increased. The relationship between the contacting period "t" offilm 3 to laminate roll 4 and thickness W of melted layer 11 issubstantially in direct proportion as shown in FIG. 3a.

As the melted area 11 thickness increases, adhesion of film 3 to metalsheet 2 during forming increases after being cooled. The relationshipbetween them is also substantially in direct proportion as shown in FIG.3b. In addition to the increase of the melted layer thickness, theincrease of the period during which film 3 is pressed to metal sheet 2multiplicably affects film 3 and its adhesion is more improved.

In the above-mentioned example, the increase of adhesion of film duringforming is explained on condition that the laminating speed is the sameas that applied in the conventional method. Conversely speaking, if theadhesion obtained by the conventional manufacturing method is deemedsufficient, the laminating can be carried out at a higher speed than isconventional. Furthermore, winding the film round the laminate rollmakes the contacting period of laminate sheet 10 to laminate roll 4longer immediately after the lamination, and the cooling effect by thelaminate roll can be fully obtained. Therefore, film 3 does not whollymelt even when metal sheet 2 coming out from the oven is heated to ahigher temperature, and the unmelted layer can reliably remain outside.Accordingly, even when the laminating is carried out at a high speed,melted layer 11 having sufficient thickness can be obtained, thusincreasing the film adhesion during forming. In this case, theorientation of the film in the unmelted layer is reduced. Between meltedlayer 11 and slightly oriented layer 12, there exists a thickness zoneor layer (not shown) where the degree of orientation gradually decreasesfrom the slightly oriented layer 12 to the melted layer 11.

Next, concrete examples and comparison examples are given and the effectof the manufacturing method of the present invention is explained.

EXAMPLES 1 TO 3

A biaxially oriented polyester thermoplastic resin film having thicknessof 25 μm was heat laminated on one side of a strip of electrolyticallychromated steel (TFS) having a thickness of 0.2 mm used for can stockusing the manufacturing apparatus as shown in FIG. 1. The temperature ofthe steel strip just before coming to the laminate rolls was about 225°C., and that of the laminate roll spontaneously cooled was about 150° C.The traveling speeds of the laminate sheet were 100, 200 and 400 m/minin Example 1, 2 and 3, respectively. Winding angle for the laminatesheet round the laminate roll was 20° in all examples.

When the laminates thus obtained were formed into a cup having adiameter of 65 mm and a height of 100 mm using a drawability tester, nofilm crack was caused in any of the examples and 4.0 to 5.6 N/10 mm ofstripping force of the film (adhering strength during forming) wasrequired to strip the film in each example. The original orientation ofthe film determined by measuring the birefringence index was about 0.09,while in the laminated film, the melted layer had the birefringenceindex of 0.01 and the thickness of about 5 to 15 μm, and the interveninglayer had the birefringence index of 0.01 to 0.05 and the thickness ofabout 3 μm.

COMPARATIVE EXAMPLES 1 TO 3

The laminating operation for Comparative examples 1, 2 and 3 wereperformed on the same conditions (the traveling speed of the laminatesheet were 100, 200 and 400 m/min, respectively) as in Examples 1-3except that the laminate sheet was not made to wind round the laminateroll but traveled downward straight. When the laminate sheet ofComparative example 3 was formed into a cup substantially the same asExample 1, a film crack was partially caused. In case of Comparativeexamples 2 and 3, no film crack was caused, but stripping force of thefilm (adhering strength during forming) were 4.0 and 2.9 N/10 mm,respectively. The melted layer had a birefringence index of 0.01 and thethickness of about 0 to 5 μm, the slightly oriented layer had abirefringence index of about 0.058 and a thickness of about 20 to 25 μm,and the intervening layer had a birefringence index of 0.01 to 0.05 anda thickness of about 3 μm. The results are shown in Tables 1 and 2.

                  TABLE 1                                                         ______________________________________                                        Example                                                                           Traveling Thickness of                                                                              Thickness of                                                                            Adhering                                  No  Speed     Melted Layer                                                                              Oriented Layer                                                                          Strength                                  ______________________________________                                        1   100 m/min 15 μm    10 μm  5.6 N/10 mm                               2   200 m/min  9 μm    16 μm  4.8 N/10 mm                               3   400 m/min  5 μm    20 μm  4.0 N/10 mm                               ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Comparative Example                                                               Traveling Thickness of                                                                              Thickness of                                                                            Adhering                                  No  Speed     Melted Layer                                                                              Oriented Layer                                                                          Strength                                  ______________________________________                                        1   100 m/min 5 μm     20 μm  4.0 N/10 mm                               2   200 m/min 2.5 μm   22.5 μm                                                                              2.9 N/10 mm                               3   400 m/min 0 μm     25 μm  0.5 N/10 mm                               ______________________________________                                    

From the results shown above, it is apparent that according to themanufacturing method of the present invention, a laminate sheet can beobtained having excellent adhering strength of the film to the metallicsheet and hardly able to be peeled off during subsequent forming, evenwhen the laminate sheet is manufactured at a high speed of 100˜400m/min.

INDUSTRIAL UTILITY

As mentioned above, according to the manufacturing method of the presentinvention, the adhering strength of the film to a metallic sheet can beimproved and it is not reduced even when the laminating operation isperformed at a high speed. According to the manufacturing apparatus ofthe present invention, the above-mentioned manufacturing method caneasily be carried out.

SUMMARY

A method of producing a laminate sheet (10) comprises the steps ofheating a continuous belt-like metal sheet (2) by a heating furnace (1),laminating a thermoplastic resin film (3)on at least one of the surfacesof the metal sheet, pressing and passing both of them between a pair oflaminate rolls (4 and 5), and thermally bonding the film (3) to themetal sheet (2), wherein the laminate sheet (1) coming out from betweenthe pair of laminate rolls (4 and 5) is pushed by a deflector roll (6)in a transverse direction so as to bias the traveling direction towardsthe laminate roll (4) which contacts film (3). The invention alsodiscloses an apparatus (A) used for this method.

What is claimed is:
 1. A manufacturing method for a laminate sheetcomprising the steps of:heating a continuous metal sheet; laminatingthermoplastic resin films on the surfaces of the metal sheet; andpassing the composite so formed between a couple of laminate rolls,pressing them, and thermally bonding said films to said metal sheet toprovide a laminate sheet, wherein said laminate sheet coming out frombetween said couple of laminate rolls is pushed aside in a transversedirection so as to bias its traveling direction to either one of saidlaminate rolls, and to prolong contact of one of the surfaces of saidlaminate sheet with one of the laminate rolls for increased cooling, andto press said laminate sheet against one of said laminate rolls toprovide a greater contacting force between one of said laminate rollsand said laminate sheet so as to improve the cooling effect when saidlaminate exiting said laminate rolls is pushed aside to one of saidlaminate rolls.
 2. A manufacturing apparatus comprising:means forsupplying and means for heating a metal sheet; means for supplyingthermoplastic resin films to opposite surfaces of said heated metalsheet; a couple of laminate rolls for pressing said metal sheet and saidthermoplastic resin films together to obtain a laminate sheet and forcooling the surfaces of said laminate sheet; a deflector roll forpushing the laminate sheet, which has passed between said laminaterolls, in a transverse direction so as to bias the traveling directionof the laminate sheet to one of the laminate rolls and provide prolongedcontact of one of the surfaces of said laminate sheet with one of thelaminate rolls for increased cooling; and a pressure roll for pressingsaid laminate sheet against said one of said laminate rolls so as toprovide a greater contacting force between one of said laminate rollsand said laminate sheet and improve the cooling effect when saidlaminate sheet which has come out through said laminate rolls is pushedaside to one of said laminate rolls.
 3. The manufacturing apparatusaccording to claim 2further comprising a guide roll for making saidtravelling direction of said laminate sheet which is biassed by saiddeflector roll back to the original travelling direction of saidlaminate sheet.
 4. The manufacturing apparatus according to claim 2,wherein said deflector roll is movably arranged in a directiontransverse to said original traveling direction of said laminate sheet.5. The manufacturing apparatus according to claim 3, wherein saiddeflector roll is moveably arranged in a direction transverse to saidoriginal traveling direction of said laminate sheet.
 6. A method formanufacturing a laminate comprising a metallic substrate and first andsecond oriented plastic films adhered to opposite surfaces of saidmetallic substrate, said method comprising:continuously passing acontinuous length of metal sheet through a heating device tocontinuously heat said metal sheet; continuously passing(1) a continuouslength of said first oriented plastic film adjacent a first laminateroll and into contact with a first surface of said metal sheet and (2) acontinuous length of said second plastic film adjacent a second laminateroll and into contact with a second surface of said metal sheet, andpassing said oriented plastic films and heated metal sheet through thenip between said first laminate roll and said second laminate roll,whereby said metal sheet and plastic films are pressed and thermallybonded together to form a laminate of said oriented plastic films andsaid metallic substrate; and continuously passing said laminate out frombetween said nip, deflecting the path of said laminate in a transversedirection toward said first laminate roll with a deflector roll to causethe surface of said first oriented plastic film opposite the surface ofsaid first plastic film adhered to said metal sheet to remain in contactwith said first laminate roll beyond said nip, and pressing saidlaminate against said first laminate roll so as to increase thecontacting force between said first laminate roll and said laminate andimprove the cooling effect when said laminate which has come out throughsaid first and second laminate rolls is deflected to said first laminateroll.
 7. A method for manufacturing a laminate comprising a metallicsubstrate and an oriented plastic film adhered to a surface of saidmetallic substrate, said method comprising:continuously passing acontinuous length of metal sheet through a heating device tocontinuously heat said metal sheet; continuously passing a continuouslength of said oriented plastic film adjacent a first laminate roll andinto contact with said metal sheet, and passing said oriented plasticfilm and heated metal sheet through the nip between said first laminateroll and a second laminate roll, whereby said metal sheet and plasticfilm are pressed and thermally bonded together to form a laminate ofsaid oriented plastic film and said metallic substrate; continuouslypassing said laminate out from between said nip and deflecting the pathof said laminate in a transverse direction toward said first laminateroll with a deflector roll to cause the surface of said oriented plasticfilm opposite the surface of said plastic film adhered to said metalsheet to remain in contact with said first laminate roll beyond saidnip; and pressing said laminate against said first laminate roll so asto increase the contacting force between said first laminate roll andsaid laminate and improve the cooling effect when said laminate whichhas come out through said first and second laminate rolls is pushedaside to said first laminate roll.